//===--- ScratchBuffer.cpp - Scratch space for forming tokens -------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the ScratchBuffer interface. // //===----------------------------------------------------------------------===// #include "clang/Lex/ScratchBuffer.h" #include "clang/Basic/SourceManager.h" #include "llvm/Support/MemoryBuffer.h" #include <cstring> using namespace clang; // ScratchBufSize - The size of each chunk of scratch memory. Slightly less //than a page, almost certainly enough for anything. :) static const unsigned ScratchBufSize = 4060; ScratchBuffer::ScratchBuffer(SourceManager &SM) : SourceMgr(SM), CurBuffer(nullptr) { // Set BytesUsed so that the first call to getToken will require an alloc. BytesUsed = ScratchBufSize; } /// getToken - Splat the specified text into a temporary MemoryBuffer and /// return a SourceLocation that refers to the token. This is just like the /// method below, but returns a location that indicates the physloc of the /// token. SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len, const char *&DestPtr) { if (BytesUsed+Len+2 > ScratchBufSize) AllocScratchBuffer(Len+2); else { // Clear out the source line cache if it's already been computed. // FIXME: Allow this to be incrementally extended. auto *ContentCache = const_cast<SrcMgr::ContentCache *>( SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc)) .getFile().getContentCache()); ContentCache->SourceLineCache = nullptr; } // Prefix the token with a \n, so that it looks like it is the first thing on // its own virtual line in caret diagnostics. CurBuffer[BytesUsed++] = '\n'; // Return a pointer to the character data. DestPtr = CurBuffer+BytesUsed; // Copy the token data into the buffer. memcpy(CurBuffer+BytesUsed, Buf, Len); // Remember that we used these bytes. BytesUsed += Len+1; // Add a NUL terminator to the token. This keeps the tokens separated, in // case they get relexed, and puts them on their own virtual lines in case a // diagnostic points to one. CurBuffer[BytesUsed-1] = '\0'; return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1); } void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) { // Only pay attention to the requested length if it is larger than our default // page size. If it is, we allocate an entire chunk for it. This is to // support gigantic tokens, which almost certainly won't happen. :) if (RequestLen < ScratchBufSize) RequestLen = ScratchBufSize; // Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file // deterministically. std::unique_ptr<llvm::WritableMemoryBuffer> OwnBuf = llvm::WritableMemoryBuffer::getNewMemBuffer(RequestLen, "<scratch space>"); CurBuffer = OwnBuf->getBufferStart(); FileID FID = SourceMgr.createFileID(std::move(OwnBuf)); BufferStartLoc = SourceMgr.getLocForStartOfFile(FID); BytesUsed = 0; } |